CD59, a Complement Regulatory Protein, Controls Choroidal Neovascularization in a Mouse Model of Wet-Type Age-Related Macular Degeneration

Abstract

We have shown that membrane attack complex (MAC) formation via the activation of the alternative pathway plays a central role in the laser-induced choroidal neovascularization (CNV). This study was undertaken to understand the role of a complement regulatory protein, CD59, which controls MAC assembly and function, in this model. CNV was induced by laser photocoagulation in C57BL/6 and Cd59a−/− mice using an argon laser. Animals from each group were sacrificed on day 1, 3, 5, and 7 postlaser. Retinal pigment epithelium-choroid-scleral tissue was examined to determine the incidence and size of CNV complex, and semiquantitative RT-PCR and Western blot analysis for CD59a was studied. Recombinant soluble mouse CD59a-IgG2a fusion (rsCD59a-Fc) protein was injected via i.p. or intravitreal routes 24 h before laser. Our results demonstrated that CD59a (both mRNA and protein) was down-regulated during laser-induced CNV. Cd59a−/− mice developed CNV complex early in the disease process. Increased MAC deposition was also observed in these Cd59a−/− mice. Administration of rsCD59a-Fc inhibited the development of CNV complex in the mouse model by blocking MAC formation and also inhibited expression of angiogenic growth factors. These data provide strong evidence that CD59a plays a crucial role in regulating complement activation and MAC formation essential for the release of growth factors that drive the development of laser-induced CNV in mice. Thus, our results suggest that the inhibition of complement by soluble CD59 may provide a novel therapeutic alternative to current treatment.

C1q as a unique player in angiogenesis with therapeutic implication in wound healing

“…Failure of C3-and C5-deficient mice to develop laser-induced CNV supports the hypothesis that C contributes to angiogenesis (12,13). Consistent with this, the degree of CNV is decreased in C3aR-and C5aR-deficient mice or in animals treated with C3aR and C5aR antagonists (11) or with recombinant CD59a-Fc, which prevents the assembly of MAC (14). However, Langer et al (15) have recently reported an inhibitory role of C on angiogenesis in a mouse model of retinopathy of prematurity.…”

Immunopathological aspects of age-related macular degeneration

“…Conversely, mice deficient in CD59 (cd59 −/− ), a negative regulator of complement, exhibit increased deposition of the C5a-9 MAC complex in CNV lesions, as well as more severe laser-induced CNV. Intraperitoneal or intravitreal administration of recombinant CD59 protein reverses this affect, leading to decreased MAC deposition, reduced expression of angiogenic factors, and dramatically decreased CNV development in the cd59 −/− mice (13% incidence of CNV versus 94% in controls) [53]. These data in murine models of laser-induced CNV support studies in human AMD that overactivity of the complement system, at least in part, mediates AMD pathogenesis, including CNV.…”

Recombinant Membrane-targeted Form of CD59 Inhibits the Growth of Choroidal Neovascular Complex in Mice

“…Evidence from both human and animal studies supports a key role for complement activation in the development of CNV (7)(8)(9)(10)(11). We demonstrated that membrane attack complex (MAC) formation via the alternative pathway activation is important for the release of angiogenic growth factors that are critical for the induction of CNV in mouse model (9).…”

“…Laser-induced mouse model of CNV in which Bruch's membrane (BM) is disrupted by laser photocoagulation is well established and is used by an increasing number of investigators (4 -7). Over the last ten years, we have noted that rodent model of laser-induced CNV has provided valuable information and contributed significantly to our understanding of the underlying mechanisms involved in the pathogenesis of new vessel growth from the choroid (7)(8)(9)(10).…”